Pilot bit with reinforcing ribs

ABSTRACT

Earth auger pilot bit is an improvement upon U.S. Pat. No. 2,773,673. The body of the bit is triangular when viewed in side elevation from one direction and narrower and thinner when viewed turned 90*. There is a &#39;&#39;&#39;&#39;fish-tail&#39;&#39;&#39;&#39; lower extremity. There are two (or more) spiral cutting blades protruding from the body and extending into the fishtail, the second blade on each side joining the leading blade of the other at the bottom of the bit to reinforce same. The improvement consists of having one or more reinforcing ribs supplementing and reinforcing the fishtail and also the leading spiral blades. The reinforcing ribs resist fracture of the bit upon severe impact and absorb wear, thereby prolonging the life of the bit.

1 June 5, 1973 2,894,726 7/1959 Weaver ct al.....................l75/392X Primary Examiner-Marvin A. Champion Assistant ExaminerRichard E.Favreau Attorney-Julian Caplan Corporation, Sunnyvale,

No. 2,773,673. The body of the bit is triangular when viewed in sideelevation from one direction and narrower and thinner when viewed turned90. There is a lower extremity. There are two (or more) spiral cuttingblades protruding from the body and extending into the fishtail, thesecond blade on each side joining the leading blade of the other at thebottom of the bit to reinforce same. The improvement consists of havingone or more reinforcing ribs supplementing and reinforcing the fishtailand also the leading spiral blades. The reinforcing ribs resist fractureof the hit upon severe impact and absorb wear, thereby prolong- 8Claims, 11 Drawing Figures Inventor: Arthur R. Winters, Fremont, Calif.

Assignee: Pengo Calif.

Filed: Aug. 28, 1971 Appl. No.: 176,773

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"HI" "Hu g? INVENTOR ARTHUR R. WINTERS 4 ATTORNE Y Patented June 5, 19733,736,996

3 Sheets-Sheet 3 IN VENTOR ARTHUR R. W/NTEIQS PILOT BIT WITH REINFORCINGRIBS This invention relates to a new and improved pilot bit having oneor more reinforcing ribs on each of the blades which protrude from thebody of the bit. The pilot bit for earth augers shown in U.S. Pat. No.2,773,673 has enjoyed wide-spread commercial success. One of theproblems encountered in use of such bit has been that when the bit issubjected to the impact of contact with hard rock the points of thefish-tail extremities tend to break, and the action of the pilot bit isaccordingly adversely affected. Another problem encountered in use ofthe bit in extremely abrasive soil is the fact that the blade whichprojects from a generally conical body wears with the passage of timeand the action is similarly impaired.

The principal purpose of the present invention is to avoid theseproblems which have heretofore been encountered. Accordingly, aprincipal object of the present invention is to provide reinforcing ribsfor each of the blades of the bit of a spiral configuration hereinafterdescribed.

Another principal feature of the present invention is to resist moreeffectively the impact which tends to break off the points of thefish-tail extremities of the pilot bit.

An optional feature of the invention is the formation of the ribs byapplication of hard metal, such as metal welded thereon or applied byhard facing. The hard ribs enhance the life of the bit.

A further feature of the use of ribs is the fact that as wear occurs thebody of the bit wears away between ribs, resulting in fingers of metalprotruding from the cutting edges of the bit. Such fingers improve thedrilling action of the bit, and this feature is further enhanced if theribs are of harder metal than the body of the bit.

In addition to the foregoing principal advantages of the invention, thepresent bit has the advantages of U.S. Pat. No. 2,773,673. Morespecifically, one of the features of the invention is that the bitbreaks the earth effectively and also diverts the spoil broken by thebit laterally and upwardly away from the center of the hole being boredso that the main auger may effectively convey the spoil.

Another feature os this invention, as in the previous patent, is theself-sharpening features of the cutting extremity or fishtail of thebit.

Still another feature of the invention is that the principal componentof the stress imposed upon the blades of the bit are in compressionrather than shear and hence the stress on the blades is diminished.

Other objects of the present invention will become apparent upon readingthe following specification and referring to the accompanying drawingsin which similar characters of reference represent corresponding partsin each of the several views.

In the drawings:

FIG. 1 is a side elevational view of the pilot bit in accordance withthe present invention.

FIG. 2 is a top plan as viewed on line 2-2 of FIG. 1.

FIG. 3 is a bottom plan view thereof.

FIG. 4 is a side elevational view taken 90 from FIG. 1 as indicated byline 4-4 of FIG. 1.

FIG. 8 is a fragmentary sectional view through a rib as exemplified bysection 8-8 of FIG. 5.

FIG. 9 is a view similar to FIG. 5 of another modified bit.

FIG. 10 is a view similar to FIG. 6 of the modification of FIG. 9.

FIG. 11 isa side elevational view of said modification rotated 90 fromthe position of FIG. 9.

The pilot bit of the present invention is a unitary casting having anupper body portion 11 which merges into a lower fish-tail extremity 12.The upper body 11 viewed in the direction of FIG. 1 is an invertedtriangle having about a 90 included angle. As viewed turned 90 in FIG.4, the body 11 is flat rather than triangular. The upper end 13 of thebit is flat and its plane is perpendicular to the axis 14 of the cone,which is also the axis of rotation of the bit, and its axis of symmetry.Top 13 resembles a parallelogram. (FIG. 2) Extending into upper end 13is a socket 16 which receives a drive lug (not shown) connected to anauger shaft. The construction of socket 16 is shown in U.S. Pat. No.2,870,995 and is not here detailed. In order to provide room for socket16, bosses 17 are formed on opposite sides of the upper body 11extending down from upper end 13 and terminating in diametricallyopposed, horizontal shoulders 18. Flats 19 are formed on the body andextending diametrically through the body between flats l9 and into thelower portion of recess 16 are holes 21. A bolt passes through the holesand also through an apertured extension (not shown) of the drive lug tosecure the pilot bit to said lug.

Only one side of the bit will be described since the opposite side isidentical.

, Blade 26 is formed protruding from upper end 13 and originates atacute outside comer 27 of the parallelogram upper end 13. The outer edge28 of blade 26 curves downwardly-forwardly in the direction of rotationof the bit (counter-clockwise as viewed in FIG. 3).

0 The length of blade 26, as viewed in plan, is approxi- FIG. 5 is aview similar to FIG. 1 of a modified bit.

FIG. 6 is a view similar to FIG. 3 of said modification. FIG. 7 is avertical sectional view of said modification taken substantially alongline 77 of FIG. 6.

mately of are. In elevation, the blade extends below the theoreticalapex of the conical body to provide the fish-tail 29 which ischaracteristic of U.S. Pat. No. 2,773,673. The fish-tail 29 isapproximately 40 percent of the total vertical height of the bit. Theextent to which the blade extends beyond the outline of the triangularbody 11 increases as the blade proceeds downward. That is, at the uppercorner 27 the blade outer edge and the body are coextensive, but as theblade proceeds downwardly the dimension by which the outer edge 28thereof protrudes beyond the theoretical triangular shape of the bodyincreases steadily.

In cross-section, blade 26 comes to a rather blunt point at its outeredge 28 and front and back flanks 31, 32 slant toward the body at anangle of about 30 and merge with the body on front and back flanks 31,32 in a radius 33. This form of cross-section of the blade givesstrength to the blade and also directs the spoil cut by the bitoutwardly and upwardly away from axis 14 so that the auger above thepilot bit can handle the spoil.

At the lower end of the leading edge of blade 26, the latter istruncated in an approximately horizontal cutting edge 34 which isdisplaced forwardly of a radius from axis 14 in the direction of theturning of the bit. The outer comer 36 of the cutting edge is positionedon a diameter. The inner edge 37 of the fish-tail slantsdownwardly-inwardly at an angle of about 45 with respect to axis 14.

The foregoing description of the outer edge 28 of blade 26 issubstantially the same as the blade of U.S. Pat. No. 2,773,673.

A feature of FIGS. 1-4 of the present invention is the provision of atrailing blade 41 which is behind leading blade 26 in the direction ofrotation of the bit. Trailing blade 41 originates at a point 42 on theouter edge 28 of the leading blade which is approximately one-half thedistance down from upper end 13. The outer edge 40 of trailing blade 41diverges from the outer edge 28 of leading blade 26 and the angle ofdivergence increases proceeding downwardly to a maximum of 1 in a planeperpendicular to axis 14 to provide rake.

The outside edge 40 of the trailing blade connects with and terminatesat the outer corner 36 of the cutting edge 28 of the opposite primaryblade 26, and thus reinforces said corner 36. The groove 46 betweenleading blade 26 and trailing blade 41 is approximately V- shaped andwith a radius at the bottom of the V, and the depth of groove 46increases proceeding downward. The cross-section of secondary blade 41is similar to that of the primary blade 26.

Thus, each side of the bit consists of two blades 26 and 41 which,proceeding toward the bottom of the bit, are oppositely divergent, thetrailing blade 41 veering off toward the opposite leading blade 26.

The horizontal cutting edge 34 of each leading blade, which takes theshock of impact in hard ground, is reinforced by reason of the fact thatthe outer corner 36 of the leading blade 26, is connected to the outercorner of the trailing blade 41 of the opposite side of the bit. On theother hand, the leading blade side edge 28 is followed in the directionof the rotation of the bit by the outer edge 40 of the trailing bladewhich is, when the bit is newly manufactured, only a slight distanceless from the axis than that of the leading blade. As the bit wears, theouter edge 28 of the leading blade wears away and part of the cuttingaction is assumed by the outer edge 40 of the trailing blade. Hence, thelife of the blades 26 and 41 and the fish-tail ends 12 of the bit areprolonged.

On the forward flank 31 of blade 26 is a plurality of reinforcing ribs47w-z which are here shown to be four in number but which may be varieddepending upon the requirements of the particular bit. As here shown,the uppermost rib 47w originates at origin 48w of the forward edge ofupper end 13 adjacent but spaced inward of corner 27 and extendsdownward along the leading face 31 of blade 26 almost straight down sothat it intersects edge 28 at terminus 49w about four-tenths of theoverall height of the bit down from upper end 13.

Next uppermost rib 47x originates at origin 48x at radius 33 aboutone-tenth the vertical height of the bit down from upper end 13. Rib 47xcurves from origin 48x at a lesser angle than spiral edge 28 andintersects edge 48 in terminus 49;: below point 42 and about sixtenthsof the height of the bit below end 13, terminus 49x being horizontallyapproximately opposite the apex of upper body 11.

Third rib 47y has its origin 48y at radius 33 about opposite terminus49w (about four-tenths of the height of the bit). Rib 47y curvesdownward about parallel to rib 47x and its terminus is about coincidentwith corner 36.

Fourth rib 471 has its origin 48z in radius 33 about opposite terminus49x and curves across the trailing flank of the opposite trailing blade49, intersecting edge 40 thereof about one-tenth the height of the bitup from edge 34.

Termini of ribs 47w, x and y are spaced apart approximatelyequidistantly along the length of edge 28.

Each rib 47 in cross-section is triangular and is of substantiallyuniform dimension throughout its length except at the extreme lower andupper ends thereof. Ribs 47w-z may be fabricated of hard metal or may behomogeneous. If of hard metal, a preferred method of fabrication is hardfacing. The parent metal is heated to a'red heat, and the leadingsurface is bombarded with a hard-face powder. Such a method is describedin U.S. Pat. No. 2,361,962 of Wall Collmonoy Corporation, and theequipment for performing the operation is sold by the said company underthe trademark Colomoray Spraywelder. Alternatively, hard-facing rods maybe welded on to the leading surface as is well understood in thehard-facing art. It is not intended that the invention be restricted toany particular means or method for forming the rib, and, indeed, the ribmay be case of the same metal as the blade.

As the blade 26 wears, the metal between the reinforcing ribs 47w-zwears away. This results in the outer edge 28 of blade 26 between ribswearing away in indentations leaving protruding fingers at the lowerends of the reinforcing ribs. The fingers augment the cutting action ofthe bit in that they, for practical purposes, comprise a plurality ofdigging points which are more effective in breaking down the structureof the soil being drilled than a single continuous blade. It is, ofcourse, true that the reinforcing ribs even when hardened eventuallywear, but being thicker than the blade edge, they wear at a slower ratethan the body 11.

A principal additional function of the reinforcing ribs 47 is tostrengthen the blades against the impact of the bit striking a hardrock. There is a tendency for the blade to be broken off on such impact.This is particularly true of the fish-tail portions 12 of the bladewhich project towards the bottom. The reinforcing ribs 47y, z materiallystrengthen said protruding fish-tails, which are inherently the weakestpart of the blades as they normally strike the hard formation first andalso are relatively unsupported by the body of the bit. Hence, a primaryfunction of at least one of the reinforcing ribs 47w-z is to strengthenthe blades 26 and the fish-tail structure.

The ribs increase the overall life of the bit sincethey reduce wear andabsorb a substantial amount of the wear of the bit particularly afterthe initial wearing of the indentions 43 between the fingers 44. Thereinforcing ribs 41, 42 also enable the bit to cut through a harderformation than would normally be the case. Or-

dinarily pilot bits of the type shown in U.S. Pat. No.

2,773,673 are not suitable for digging through rock, but the presentpilot bit will bore through rock at least if the rock is not too hard.

In the form of the invention shown in FIGS. 5-8, on the leading flank31a of leading blade 26a (in the normal direction of rotation of thebit, which is counterclockwise as viewed in FIG. 6), a first reinforcingrib 51 is formed commencing at the outer comer 36a of cutting edge 34aand extending substantially straight upwardly on said leading flankparallel to the axis of rotation 14 to a terminus 52 about one-half theoverall height of the bit up from edge 34a. Said rib 51 in crosssection(see FIG. 8) is triangular and is of substantially uniform dimensionthroughout its length except at the extreme lower and upper endsthereof. Rib 51 may be fabricated of a hard metal or may be homogeneous,as is the case with ribs 47w-z.

In the form of the invention shown in FIGS. 9-11, a modifiedconstruction is shown. In this version of the invention, a trailingblade 41b is located behind the leading blade 26b in the direction ofrotation of the bit, as in FIGS. 1-4. No reinforcing ribs correspondingto ribs 47w-z vare employed. However, a reinforcing rib 51b is formed onthe leading face of the fish-tail 29b of the leading blade 26b. Theposition and shape of rib 51b corresponds to rib 51 of FIGS. 5-8.

In other respects, the modification of FIGS. 5-8 and FIGS. 9-11 aresubstantially the same as in the modifications of FIGS. 1-4 and the samereference numerals followed by the subscript a and b respectively, areused to designate corresponding elements.

What is claimed is:

l. A pilot bit for an earth auger comprising a body having a top, saidbody having an upper portion which is of an approximately invertedtriangle shape in side elevation viewed in one direction and narrowerand substantially rectangular viewed rotated 90 and having blades atangularly spaced positions on the exterior of said body, each said bladeoriginating at said top and extending downwardly in spiral shape ofabout 180 arcuate length on the outside of said body, each said bladehaving a leading face and a trailing face in the normal direction ofrotation of said bit when said bit is digging in the earth, theprojection of said blade outward gradually increasing as said bladeextends downward, said blade extending below the apex of the triangle ofsaid body in a fish-tail and formed with a cutting edge parallel to, butspaced outward of, a diameter of said body, and a plurality ofreinforcing ribs on said leading face of said blade, each said ribhaving an origin spaced inward of the outer edge of said blade andformed in a downwardly curving spiral and having a terminus on saidouter edge.

2. A bit according to claim 1 in which each said rib is approximatelytriangular in cross-section.

3. A pilot bit according to claim 1 in which said body is formed withsecondary blades on the exterior of said body, each said secondary bladeoriginating on the outside edge of one of said first-mentioned bladespartway down from said top, each secondary blade of spiral shape andgradually diverging at an angle rearward of said first-mentioned bladeto which it is connected and increasing in projection from said body assaid secondary blade extends downward and also increasing in distancebehind said first-mentioned blade as said blades extend downwardly, saidsecondary blade extending below the apex of said body in a secondaryfish-tail which joins at its bottom end with the outer corner of thecutting edge of the first-mentioned fish-tail of the first-mentionedblade opposite that to which said secondary blade is connected, saidreinforcing ribs being located on. the leading face of saidfirst-mentioned blade.

4. A bit according to claim 1 in which said one rib has its terminus onsaid cutting edge of said fish-tail.

5. A bit according to claim 4 in which another of said ribs is on theleading face of one said fish-tail and has its terminus on the trailingface of the, next blade.

6. A pilot bit for an earth auger comprising a body having a top, saidbody having an upper portion which is triangular in side elevationviewed in one direction and narrow and substantially rectangular viewedrotated and having blades at angularly spaced positions on the exteriorof said body, each said blade originating at said top and extendingdownwardly in spiral shape of about arcuate length on the outside ofsaid body, each said blade having a leading face and a trailing face inthe normal direction of rotation of said bit when said bit is digging inthe earth, the projection of said blade outward gradually increasing assaid blade extends downward, said blade extending below the apex of thetriangle of said body in a fish-tail and formed with a cutting edgeparallel to, but spaced outward of, a diameter of said body and a hardtriangular reinforcing rib on said fish-tail extending up from saidcutting edge centrally of the leading face of said fishtail aboutone-half the overall height of said bit.

7. A pilot bit according to claim 6 in which each said reinforcing ribis of approximately triangular crosssection.

8. A pilot bit according to claim 6 in which said body is formed withsecondary blades on the exterior of said body, each said secondary bladeoriginating on the outside edge of one of said first-mentioned bladespartway down from said top, each secondary blade of spiral shape andgradually diverging at an angle rearward of said first-mentioned bladeto which it is connected and increasing in projection from said body assaid secondary blade extends downward and also increasing in distancebehind said first-mentioned blade as said blades extend downwardly, saidsecondary blade extending below the apex of said body in a secondaryfish-tail which joins at its bottom end with the outer corner of thecutting edge of the first-mentioned fish-tail of the first-mentionedblade opposite that to which said secondary blade is connected, saidreinforcing rib being located on the leading face of saidfirst-mentioned blade.

* l I i

1. A pilot bit for an earth auger comprising a body having a top, saidbody having an upper portion which is of an approximately invertedtriangle shape in side elevation viewed in one direction and narrowerand substantially rectangular viewed rotated 90* and having blades atangularly spaced positions on the exterior of said body, each said bladeoriginating at said top and extending downwardly in spiral shape ofabout 180* arcuate length on the outside of said body, each said bladehaving a leading face and a trailing face in the normal direction ofrotation of said bit when said bit is digging in the earth, theprojection of said blade outward gradually increasing as said bladeextends downward, said blade extending below the apex of the triangle ofsaid body in a fish-tail and formed with a cutting edge parallel to, butspaced outward of, a diameter of said body, and a plurality ofreinforcing ribs on said leading face of said blade, each said ribhaving an origin spaced inward of the outer edge of said blade andformed in a downwardly curving spiral and having a terminus on saidouter edge.
 2. A bit according to claim 1 in which each said rib isapproximately triangular in cross-section.
 3. A pilot bit according toclaim 1 in which said body is formed with secondary blades on theexterior of said body, each said secondary blade originating on theoutside edge of one of said first-mentioned blades partway down fromsaid top, each secondary blade of spiral shape and gradually divergingat an angle rearward of said first-mentioned blade to which it isconnected and increasing in projection from said body as said secondaryblade extends downward and also increasing in distance behind saidfirst-mentioned blade as said blades extend downwardly, said secondaryblade extending below the apex of said body in a secondary fish-tailwhich joins at its bottom end with the outer corner of the cutting edgeof the first-mentioned fish-tail of the first-mentioned blade oppositethat to which said secondary blade is connected, said reinforcing ribsbeing located on the leading face of said first-mentioned blade.
 4. Abit according to claim 1 in which said one rib has its terminus on saidcutting edge of said fish-tail.
 5. A bit according to claim 4 in whichanother of said ribs is on the leading face of one said fish-tail andhas its terminus on the trailing face of the next blade.
 6. A pilot bitfor an earth auger comprising a body having a top, said body having anupper portion which is triangular in side elevation viewed in onedirection and narrow and substantially rectangular viewed rotated 90*and having blades at angularly spaced positions on the exterior of saidbody, each said blade originating at said top and extending downwardlyin spiral shape of about 180* arcuate length on the outside of saidbody, each said blade having a leading face and a trailing face in thenormal direction of rotation of said bit when said bit is digging in theearth, the projection of said blade outward gradually increasing as saidblade extends downward, said blade extending below the apex of thetriangle of said body in a fish-tail and formed with a cutting edgeparallel to, but spaced outward of, a diameter of said body and a Hardtriangular reinforcing rib on said fish-tail extending up from saidcutting edge centrally of the leading face of said fish-tail aboutone-half the overall height of said bit.
 7. A pilot bit according toclaim 6 in which each said reinforcing rib is of approximatelytriangular cross-section.
 8. A pilot bit according to claim 6 in whichsaid body is formed with secondary blades on the exterior of said body,each said secondary blade originating on the outside edge of one of saidfirst-mentioned blades partway down from said top, each secondary bladeof spiral shape and gradually diverging at an angle rearward of saidfirst-mentioned blade to which it is connected and increasing inprojection from said body as said secondary blade extends downward andalso increasing in distance behind said first-mentioned blade as saidblades extend downwardly, said secondary blade extending below the apexof said body in a secondary fish-tail which joins at its bottom end withthe outer corner of the cutting edge of the first-mentioned fish-tail ofthe first-mentioned blade opposite that to which said secondary blade isconnected, said reinforcing rib being located on the leading face ofsaid first-mentioned blade.